Common power supply for precipitator banks with individual control



Dec. 24, 1957 Filed July 18, 1955 H. KLEMPERER COMMON POWER SUPPLY FOR PRECIPITATOR BANKS WITH INDIVIDUAL CONTROL 2 Sheets-Sheet 1 Common Power Sago/y F'lq. I

- INVENTOR Hans K L empemr NEY . 24, 1957 H. KLEMPERER COMMON POWER SUPPLY FOR PRECIPITATOR BANKS IITH INDIVIDUAL CONTROL 2 Sheets-Sheet 2 Filed July 18,. 1955 INVENTOR Hans Klemperer k m 3 M .5 388mm Q Unite Staes Patent COMNION POWER SUPPLY FOR PRECIPITATOR BANKS WITH INDIVIDUAL CONTROL Hans Klernpercr, Belmont, Mass., assignor, by rnesne assignments, to APRA Precipitator Corporation, New York, N. Y., a corporation of Delaware Application July 18, 1955, Serial No. 522,479

6 Claims. (Cl. 1837) The present invention relates to electrostatic precipitators for the removal from combustion or other impure gases of fine solid particles or impurities and is concerned particularly with improved means for automatically controlling the application of charging voltages to the precipitator electrodes during the particle collecting and cleaning or discharge cycles of such precipitators.

The precipitator in which the invention is embodied effects removal of impurities without interruption from a continuously flowing column of any impure gases by electrostatic means incorporated in apparatus providing an ionizing section or zone followed by a collecting section or zone in which the particles previously electrostatically charged in the ionizing zone are deposited and collected on a suitable collecting surface. The precipitator is provided with collecting sections having a total cross sectional area for flow of gases greater than that required for flow of the gas column to be treated so that less than the total number of gas channels provided are utilized at a given time while the remainder of the channels are in a cleaning zone outside the path of flow of the gas column in order that the collecting surfaces may be cleaned without interrupting the gas cleaning function of the apparatus as a whole. In particular the invention contemplates apparatus of the kind described in which means are provided for automatically reducing or interrupting the current to the charged elements of the precipitator prior to the cleaning period at which time the current may be completely cut off. The current is partially restored in a transition period and the charged elements have the full current again supplied thereto as they fully resume their precipitating function.

A salient feature of the present invention is that a common power source is provided for all of the sectors or electrode banks comprising the precipitator and individual power transmitting means are interposed be tween this common power supply and the individual electrode banks for controlling the supply of current to the electrode banks. Alternatively, the electrode banks of the precipitator may be divided into several groups each including several banks and a common power supply provided for each group; that is, there being several power supplies for the entire precipitator instead of a single common power supply.

In the drawings:

Figure 1 is a schematic view of a gas cleaning system incorporating a common power supply with individual current transmission and control means for the various electrode banks in accordance with the present invention;

Figure 2 is a schematic wiring diagram of the power transmission and control means for a single electrode bank; and

Figure 3 is a fragmentary illustration of an alternative transmitter arrangement for one electrode bank.

Referring now more particularly to the precipitator shown diagrammatically in the upper part of Figure 1,

' the reference character It indicates a duct delivering ice gases containing impurities from a furnace or other apparatus and 11 is a discharge duct for carrying away the cleaned gases. Between ducts 10 and 11 a stationary precipitator housing 12 is located. The housing 12 includes an inner cylindrical shell spaced from the outer housing and joined thereto by a plurality of radially extending partitions to divide the annular space between the shells into a series of sector-like compartments of which four designated 13, 14, 15, 16 appear in Figure l. The collecting surface is provided by a plate structure forming in each compartment a bank comprising a multiplicity of open ended gas channels which may be of hexagonal cross section. Each of the gas channels is traversed longitudinally by a centrally located electrode 18. Current is supplied to each compartment through individual feeders designated 20, 21, 22, 23 in Figure 1, so that the electrodes 18 may be electrically charged. The ionizing section is similar to the collector section previously described, the radial partitions that form the compartments being coextensive in length with the shells of the casing structure so that the ionizing section as well as the collecting section is divided and located in a series of compartments, the several parts of the ionizing section being also energized through the feed connections 20 to 23.

The housing is formed to provide a chamber 34) to which the gas inlet 10 leads and communicating through an annular opening with the annular space in which the banks of electrodes and collecting surfaces respectively are located. Within this chamber there is located a rotatably mounted hopper 32 projecting at its lower and through a suitable sealed opening 33 in the casing structure, being carried by a suitable bearing and having an external discharge outlet 34.

At the upper end of the shell structure a rotatably mounted casing 35 is provided, which comprises a sectorshaped wing providing a chamber housing, a cleaning element in the form of a pipe 38 rotatable along with the casing 35 by means of the suitable gearing. Pipe 38 is connected to a source of high pressure fluid, such as hot air. The casing 35 operates to isolate a compartment and/ or bank to be cleaned from the compartments through which gas is flowing and in the same manner the hopper effects this isolation at the lower end of the apparatus, and it will be evident that as the hopper 32 and casing 35 are rotated electrode banks in different compartments can be successively cleaned without interruption to the flow through the apparatus or" the gas to be cleaned.

The foregoing precipitator structure is more fully described in the patent to Per Hilmer Karlsson, No. 2,582,133, dated January 8, 1952.

A single power pack 40 is provided to supply current to all of the electrode banks comprising the precipitator through a line 41 connecting with the individual power control devices 24 to 27 which feed the related electrode banks through the lines 20 to 23 as mentioned above. The transmission and control devices 24 to 27 include electronic tubes to which a preset biasing voltage is applied through a line 42. The adjustment of this voltage may be efiected at the power pack 49, as by means of the potentiometer 43.

Figure 2 shows a power transmission and control means that is individual to one of the various electrode banks of the precipitator. As indicated in Figure 2 the current for charging the electrodes of a single precipitator bank is taken from the common power supply line 41 through a branch 44 leading to the filament 45 of a triode 46. The common grid biasing voltage is supplied through the line 42 at the value set by the potentiometer 43 and passes through a line 47 with further individual adjustment of the biasing voltage being efiected through a,

potentiometer 48. This provides an individual adjustment for each bank of the voltage applied through a line 54) which includes a resistance 51 connected to the grid 52 of the triode. At the value set by the potentiometer 43 in common for all of the electrode banks supplied by the power pack 40 and as modified for the individual electrode banks by the related potentiometer 48 the triode as for any bank functions to pass the charging current to the electrodes of the particular bank.

During the operation of the precipitator as a whole continuous cleaning of the electrode banks is effected and when any particular bank is to be cleaned of accumulated dust particles by the cleaning device 33 the current to the electrodes is first reduced and then cut oif through the operation of a rotary switch 60 operated in unison with the cleaning device. The switch 60 has contacts 6% to 6%! individual to each electrode bank so that shortly before cleaning is to be done the rotary switch causes energization of a relay 61 for that bank. The relay closes the contacts 62 in a line 63 leading to the grid 52 of the triode 46 through a resistance 6d of lower value than the resistance 51 in the line 50. This line 63 is also connected to the potentiometer 48 through an adjustable slide 64 at a point closer to the connection of the other adjustable slide 65 of potentiometer 43 to the feed line 47. As a consequence a higher voltage is applied to the grid 52 of triode 46 than normally applied through the line and this over-riding voltage reduces the capacity of the triode 46 to transmit charging current to the electrodes with the result that this current is reduced as the cleaning period for the electrode bank approaches.

When the cleaning operation of the electrode bank is to take place the rotary switch 60 effects energization of a relay 67 through contacts dtle, 697, 60g or 60h, and the relay contacts 58 upon closing connect the triode grid 52 through a line "Til including a resistance 71 of still lower value to the feed line 47. A still higher biasing voltage is thus applied to the grid 52 of the triode 46 and as a consequence the tube becomes unable under these conditions to transmit current and, consequently, the current normally supplied to the electrodes of the related bank in the precipitator is completely out off.

Figure 2 also shows a resistance 75 in the line 44 connecting the filament 45 of the triode 46 with power line 41 and through power pack all to ground. A coil 76 is connected across this resistance 75 so as to be affected by the voltage drop across the resistance. When flashovers occur within the electrode bank the voltage drop across the resistance 75 becomes such that the relay '76 is energized and as its contacts '77 engage the grid 52 is connected through the line 7th, the resistance '71 of the lines 7% and 72 to the high voltage bias line 47. The effect is the same as when the relay contacts 6% engage and the biasing voltage applied to the grid 62 is such that on occurrence of fiashovers the current supplied to the electrodes of that bank is completely cut off until the flashover disappears.

To recapitulate, all or several precipitator sectors are supplied by a common power supply 4%. Switching and voltage adjustments are performed by electronic devices, for instance, transmitter type electronic tubes 46 in the high voltage lines to the individual sectors. The power pack h"; supplies a common bias voltage to all transmitter tubes. This bias is several hundred volts negative With respect to the cathodes 45 of the transmitter tubes. The bias voltage is connected to the grids of the transmitter tubes. Common adjustment is performed in the power supply cubicle by potentiometer if), individual sector adjustment is done at the grids by means of potentiometer adjustment at 4%. Cleaning and transition voltages are controlled by the rotary switch 60 through relays 67 and (all and their conta ts 68 and 62 respectively. Series resistors 7.1, 85 i 51 are dimensioned so that the current in the cleaning line through 71 overrides that of 64 i and that in turn overrides SI. in the operating line. High voltage insulation has to be provided between coils and contacts of relays 67 and 61.

Automatic flashover suppression is provided by inductive feedback in the cathode line 44. The fiashover builds up voltage across inductance 75A which increases the negative grid bias of the transmitter tube as to full or near cutoff. The power stored in the inductance is discharged by an inverse tube fill, which time delay prevents the transmitter tube from oscillating. Additional protection is provided by relay 76 which operates if a flashover should hang on and applies off bias to the grid 52 through contact 77. A high voltage fuse 81 is located in the anode line to protect the tube against mechanical shorts in the sector.

As illustrated in Figure 3 a tetrode type transmitter tube is applicable as an alternate to the triode shown in Figure 2. In that case an additional positive bias has to be provided through 88 for the second grid $5 of the tube. The tetrode is a current limiting device in itself; therefore stabilizing and fiashover suppressing means 75A, inverse tube St), relay 76 can be dispensed with. As the current is limited by the tetrode 8d, flashovers will be blown out by the gas velocity in the sector.

What is claimed is:

1. In an electrostatic precipitator; a number of separate banks of electrodes; a single power unit associated with said electrode banks for supplying a high voltage current thereto, individual grid-controlled electronic valve means connected with said power supply unit and each associated with an individual electrode bank for separately controlling the current supply to said electrode bank independently of other electrode banks; means for applying a biasing voltage to the grid control element of each electronic valve means; means for individually adjusting the biasing voltage for each valve means; means for applying an over-riding high voltage to the grid element of each valve means; and means responsive to a condition reflecting the operation of said precipitator for rendering the related electronic valve means less effective to transmit the charging voltage to the related electrode bank and to thereby reduce the current supplied to said electrode bank.

2. In an electrostatic precipitator; a number of separate banks of electrodes; a single power unit associated with said electrode banks for supplying a high voltage current thereto, individual grid controlled electronic valve means connected with said power supply unit and each associated with an individual electrode bank for separately controlling the current supply to said electrode bank independently of other electrode banks; means for applying a biasing voltage to the grid control element of each electronic valve means; means for individually adjusting the biasing voltage for each valve means; means for applying an over-riding negative high voltage to the grid element of each valve means; means for cyclically cleaning each electrode bank; and means operable in synchronism with said cleaning means for applying said high voltage to the grid of the electronic valve means associated with the electrode bank with which said cleaning means is in determined cyclic relation for rendering the related electronic valve means ineffective to transmit the charging voltage to the related electrode bank and to thereby reduce the current supplied to said electrode banks.

3. in an electrostatic precipitator; a number of separate banks of electrodes; at single power unit associated with said electrode banks for supplying a high voltage current thereto, individual grid controlled electronic valve means connected with said power supply unit and each associated with an individual electrode bank for separatcly controlling the current supply to said electrode bank independently of other electrode banks; means for applying a biasing voltage to the grid control element of each electronic valve means; means for individually adjusting the biasing voltage for each valve means; means for applying an over-riding negative high voltage to the grid element of each valve means; means for cyclically cleaning each electrode bank; and means operable in synchronism with said cleaning means for applying said high voltage to the grid of the electronic valve means associated with the electrode bank with which said cleaning means is in determined cyclic relation for rendering the related electronic valve means ineiiective to transmit the charging voltage to the related electrode bank and to thereby reduce the current supplied to said electrode banks; and means for applying a still higher biasing voltage to the grid of the electronic valve means associated with a particular bank of electrodes when said cleaning means is in a difierent cyclic relation with said bank of electrodes for discontinuing the supply of high voltage current to the electrodes of said bank.

4. In an electrostatic precipitator; a number of separate banks of electrodes; a single power unit associated with said electrode banks for supplying a high voltage current thereto, individual grid controlled electronic valve means connected With said power supply unit and each associated with an individual electrode bank for separately controlling the current supply to said electrode bank independently of other electrode banks; means for applying a biasing voltage to the grid control element of each electronic valve means; means for individually adjusting the biasing voltage for each valve means; means for applying an over-riding negative high voltage to the grid element of each valve means; means for cyclically cleaning each electrode bank; and means operable in synchronism with said cleaning means for applying said high voltage to the grid of the electronic valve means associated with the electrode bank with which said cleaning means is in determined cyclic relation for rendering the related electronic valve means inefiective to transmit the charging voltage to the related electrode bank and to thereby reduce the current supplied to said electrode banks; and means associated with a particular bank of electrodes and responsive to occurrence of a flashover therein for ap plying a still higher biasing voltage to the grid of the electronic valve means associated with said bank so as to render said electronic valve means inoperative to transmit the high voltage charging current to the electrodes of said bank.

5. In an electrostatic precipitator; a plurality of separate banks of electrodes; a single power unit associated with a number of electrode banks less than the total of banks comprised in the precipitator for supplying a high voltage current to said number of electrode banks; individal tri-element electronic Valve means connected With said power supply unit and With individual electrode bank for separately controlling the current supply to said electrode bank independently of other electrode banks; means for applying a biasing voltage to the grid element of each electronic valve means; means for individually adjusting the biasing voltage for each valve; means for applying over-riding high voltage to the grid element of each valve means; means for cyclically cleaning each electrode bank; and means operable in synchronism with said cleaning means for applying said high voltages to the grid of the electronic valve means associated With the electrode bank with which said cleaning means is in determined cyclic relation for rendering the related electronic valve means ineffective to transmit the full charging voltage to the related electrode bank and to thereby reduce and subsequently discontinue the supply of high voltage charging current to said electrode bank.

6. In an electrostatic precipitator; a plurality of separate banks of electrodes, a single power unit associated with a number of electrode banks less than the total of banks comprised in the precipitator for supplying a high voltage current to said electrode bank; an individual valve means connected with said power supply unit and with one of said electrode banks for controlling the current supply to said electrode bank independently of other electrode banks; means for cyclically cleaning each electrode bank; means operable in synchronism with said cleaning means for rendering the valve means associated With the electrode bank with which said cleaning means is in determined cyclic relation ineifective to transmit the full charging current to the related electrode bank and to thereby reduce and subsequently discontinue the supply of charging current to said bank.

References Cited in the file of this patent UNITED STATES PATENTS 2,010,599 Levy Aug. 6, 1935 2,672,947 Kemperer Mar. 23, 1954 FOREIGN PATENTS 144,557 Sweden Mar. 25, 1954 551,416 Germany May 31, 1932 

